\documentclass[tikz, border=2mm]{standalone}

\begin{document}
\begin{tikzpicture}[scale=1]
	\foreach \y [count=\ny from 0] in {0.5,1.5,...,49.5} {
			\foreach \x [count=\nx, evaluate=\x as \num using int(\nx+10*\ny)] in {0.5,1.5,...,19.5} {
					\pgfmathsetmacro{\R}{random(0,10000)/10000}%
					\pgfmathsetmacro{\G}{random(0,10000)/10000}%
					\pgfmathsetmacro{\B}{random(0,10000)/10000}%
					\definecolor{MyColor}{rgb}{\R,\G,\B}%
					\node[fill=MyColor,inner sep=0.1cm,outer sep=0pt,anchor=center, minimum size=1cm] at (\x,-\y) {\num};
				}
		}
\end{tikzpicture}
\end{document}
